Large grain smokeless powder



Patented Apr. 17, 1951 LARGE GRAIN SMOKELESS POWDER Ralph F. Preckel, Wilmington, DeL, assignor, by mesne assignments, to the United States of America as represented by the Secretary of War No Drawing. Application November 19, 1945, Serial No. 629,709

1 Claim. 1

This invention relates to an improved large grain smokeless powder and, more particularly, to a large grain smokeless powder having cellulose acetate inhibitor strips bonded thereto by an improved adhesive.

Plastic strips have been glued to the surface of large grain smokeless powder in order to control the burning area and also to act as spacers to prevent the powder from contact with the wall of the device in which it is .burned. These strips have been applied to the ends of the powder grains, to the sides of cylindrical sticks, and also to the arms of a cruciform stick of smokeless powder. improved ballistics have been obtained by reducing the initial surface of the powder by gluing inhibitor strips of cellulose acetate to the powder surface. The firmness with which the inhibitor strip is adhered to the powder is very important, since a single poorlyadhered strip may seriously affect the ballistics of the weapon or the behavior of the device in which the powder is burned. It has been found undesirable to have air bubbles between the strip and the powder or to have a crack along the edge of the strip which will permit access of the flame to a free surface of powder underneath the strip. Such defects tend to nullify the effect of the strip.

Many substances which are ordinarily used as 2. There follow some examples which illustrate specific embodiments of the'invention:

EXAMPLES 1 TO- 5 The adhesive compositions given in the table were applied to a cellulose acetate strip which wa then placed on an arm of a cruciform grain of double base smokeless powder. The cellulose acetate strips used had a thickness of 0.1 inch and had the following composition:

Per cent Cellulose acetate 74 Dibutyl phthalate 4 Diethyl phthalate 16 Dimethyl phthalate 6 Acetic acid content 56.557.5% viscosity 150-250 seconds i e., the time of fall of a 5/10-incl1 steel ball through 10 inches of a solution of cellulose acetate in a mixture of 9 parts of methylene chloride to 1 part of alcohol in a 1-inch tube at C.

The smokeless powder had the following composition:

Per cent Nitrocellulose 52.15 Nitro'glycerin 43.00 Diethyl phthalate 3.00 Diphenylamine 0.60 Potassium nitrate 1.25

The results are given in the following table:

Table A o t s r i fi Perm} R k dhesive omposition Time 0 et Up ac inency 0 Omar s amples ness Bond l Diacetcne Alcohol Less than two minutes Good Good. Pozivger pulled after ours. Cellulose Acetate 57 1 2 {lc)ialcetone Alcohol 957% Very good el ulose Acetate l5 3 {Dlacetone Alcohol }Less than three minutes. do Good.

Cellulose Acetate 20 4, Diacetone Alcohol 55% Less than five minutes" do do llr lethylEtlyl Ketone 25% riacetm 5 Diacetone Al ohol 50% mmutes 1 The cellulose acetate had an acetic acid content of 55% and a viscosity of 3 seconds.

It is noted that in each case the initial tackiness of the adhesive was good and the bond formed was strong. After the strip had been adhered to the grain for 24 hours, an attempt was made to pull the inhibitor strip away from the powder grain. When sufficient force was used, a line of separation was produced in the powder beneath the strip. This shows that the bond formed was stronger than the powder.

As illustrated in the above examples, diacetone alcohol, either alone or mixed with various other substances, forms an excellent bondbetween cellulose acetate strips and smokeless powder grains. Substances which may be added to the diacetone alcohol include cellulose acetate. triacetin, methyl ethyl ketone, acetone, nitrocellulose, diethyl phthalate, dibutyl phthalate, acetol, acetonyl acetone, ethyl acetoacetate, and other diketones, keto esters and keto alcohols.

When cellulose acetate dissolved in diacetone alcohol is used as an adhesive, a desirable bead is formed along the edges of the strip. The cellulose acetate may be added to diacetone alcohol up to its limit of solubility.

The cellulose acetate inhibitor strips may be made from any cellulose acetate which is soluble in the usual organic solvent. The cellulose acetate should have an acetic acid content between 51 and 59%. The strips may contain between 60 and 90% of cellulose acetate and from 40 to 10% plasticizers. Suitable plasticizers include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, methyl phthalyl ethyl glycolate, p-toluene sulfonamid, p-toluene sulfonate, triacetin, tripropionin, dibutyl tartrate and triphenylphosphate.

The powder compositions for use in accordance with the present invention maybe varied considerably from the specific powder composition set forth in the examples. By proper variation of the content and type of nitrocellulose, the content and type of nonvolatile plasticizer and the content and type of other ingredients, operable powders of considerable variety may be made. However, the present invention is primarily directed to compositions containing a substantial amount of nonvolatile plasticizer. For example, the powder may contain from 35 to about 60% nitroglycerin and/ or similar organic nitrate, such as diethylene glycol dinitrate or diethanol nitramine dinitrate (di(2 nitroxyethyDnitra mine), as the nonvolatile plasticizer, from to about 5% inorganic salts, from about 0.5 to about stabilizer, from about 0.01 to about 2.0% opaquing agent, and from about 40 to about'65% of nitrocellulose.

The large grain smokeless powder grains formed in accordance with this invention are used in jet-propelled devices, such as rockets, airplane starters, assisted take-off devices, catapult devices, gas-producing devices, and the like, including any devices which derive translational o1 rotational energy at least partly from the action produced from the issuance at relatively high speed of fluid medium from an opening in the device.

The diacetone alcohol compositions described in accordance with this invention are excellent adhesives for applying cellulose acetate strips to smokeless powder grains. These compositions are quick-setting and form strong permanent bonds between cellulose acetate and the powder. They do not adversely afiect the stability of the powder and are easily applied without the formation of air bubbles between the strip and the powder; they are nontoxic, evaporate only relatively slowly on standing, and have excellent initial tackiness.

Where, in the specification and in the ap pended claims, the term large grain smokeless powder is used, it is meant a smokeless powder having a web thickness of more than 0.20 inch. The web thickness is defined as the least burning thickness from the edge of one surface to the edge of another surface, regardless of the configuration of the grain.

What I claim and desire to Patent is:

A large smokeless powder grain having a cellulose acetate inhibitor strip tightly bound to the surface thereof by an adhesive region formed at the interface between the powder and the strip by means of a composition consisting essentially of a solution of about 5% cellulose acetate dissolved in diacetone alcohol acting as protect by Letters a plasticizing solvent for both the powder and the strip.

RALPH F. PRECKEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 778,788 Maxim Dec. 27, 1904 1,354,442 Woodbridge et a1. Sept. 20, 1920 1,793,915 Dreyfus Feb. 24, 1931 2,044,356 Keeran June 16, 1936 2,229,208 Holm et a1. Jan. 21, 1941 FOREIGN PATENTS Number Country Date 27,197 Great Britain Nov. 30, 1897 of 1896 502,560 France Feb. 24, 1920 OTHER REFERENCES Brady: Materials Handbook, McGraw-Hill Book Company, 1944, pages 6, and 9 and 10. (Copy in Division 30.)

Hackhs Chemical Dictionary, by J. Grant, third edition, The Blakiston Company, Philadelphia, Pennsylvania, page 263, 1944. (Copy in Division 43, U. S. Patent Office.) 

